1. Field of the Invention
The present invention relates to a method of determining voltage conditions of fuel cell vehicles.
2. Description of Related Art
A typical example of known solid polymer membrane fuel cells has a cell in which a fuel electrode (i.e., an anode) and an air electrode (i.e., a cathode) are provided on either side of a solid polymer electrolyte membrane, and a plurality of such cells are stacked to form a stack. In this structure, hydrogen is supplied as a fuel to the fuel electrode, while air is supplied as an oxidizer to the air electrode, so that hydrogen ions, generated by catalytic reaction at the fuel electrode, pass the solid polymer electrolyte membrane and reach the air electrode, thereby producing an electrochemical reaction between the hydrogen ions and oxygen at the air electrode, and generating electric power.
In a typical example of known fuel cell vehicles in which a fuel cell as explained above is mounted as a driving (force) source, a battery device such as a capacitor or a battery is provided for storing electrical energy generated by the fuel cells and for sending or receiving electrical energy to and from a motor for running the vehicle.
In such fuel cell vehicles, the battery device is connected in parallel to the fuel cell via an output controller for controlling the current and the voltage output from the fuel cell. The output control operation, for example, electric power conversion of an output controller which includes a DC-DC converter or the like, may be controlled in accordance with the running state of the fuel cell vehicle, the operation state of the fuel cell, or the condition of the battery device (see, for example, Japanese Unexamined Patent Applications, First Publications Nos. H11-067253 and 2001-204106).
In the above-described fuel cell vehicles, electric power conversion, executed by an output controller having a DC-DC converter or the like, causes some amount of power loss. Therefore, it is required to reduce frequency of the operation of the output controller so as to prevent increase in the power loss.